Surface light source device and backlight unit having the same

Abstract

There is a provided a surface light source device comprising: a light source body having an inner space therein in which a discharge gas is contained; a plurality of electrodes formed on the light source body in such a manner as to electrically divide the inner space into at least three blocks and applying discharge voltages to the blocks; and a driving unit sequentially applying the discharge voltages to the blocks through the electrodes in synchronization with a video signal of an external display device. The light source body may have a plurality of discharge spaces or a single discharge space therein. In accordance with the present invention, the surface light source device sequentially applies the discharge voltages to the blocks, and thereby can reduce an after-image occurring in a liquid crystal display device. Further, the surface light source device is driven with a duty ratio varied depending on brightness of the video signal, and thereby integrated power consumption can be reduced and a contrast ratio can be improved.

1 . A surface light source device comprising:
 a light source body having an inner space therein in which a discharge gas is contained;   a plurality of electrodes formed on the light source body in such a manner as to electrically divide the inner space into at least three blocks and applying discharge voltages to the blocks; and   a driving unit sequentially applying the discharge voltages to the blocks through the electrodes in synchronization with a video signal of an external display device.   
     
     
         2 . The surface light source device of  claim 1 , wherein the electrodes are formed at both ends of the blocks, and the driving unit applies anti-phase voltages to both ends of the blocks through the electrodes. 
     
     
         3 . The surface light source device of  claim 1 , wherein the driving unit applies the discharge voltages in such a manner that an end point when applying a discharge voltage to a first block ends is at the same time as a start point of a vertical frequency of the video signal. 
     
     
         4 . The surface light source device of  claim 1 , wherein the driving unit applies the discharge voltages in an impulse waveform with a frequency of 20˜60 kHz and an on-time of 0.1˜10 μs. 
     
     
         5 . The surface light source device of  claim 1 , wherein the driving unit applies the discharge voltage to each block according to a pulse width modulation signal with a duty ratio of 50% or less. 
     
     
         6 . The surface light source device of  claim 5 , wherein the driving unit varies the duty ratio within 10˜50%, depending on brightness of the video signal. 
     
     
         7 . The surface light source device of  claim 5 , wherein the duty ratio is within 25 to 40%, voltage pulses with a frequency of 1 kHz or more are applied during an on-duty period, and the number of the voltage pulses is controlled depending on brightness of the video signal. 
     
     
         8 . The surface light source device of  claim 1 , wherein the inner space is partitioned into a plurality of discharge spaces and a gap between the electrodes is wider than a gap between the discharge spaces. 
     
     
         9 . The surface light source device of  claim 1 , wherein the light source body comprises a plurality of discharge spaces. 
     
     
         10 . The surface light source device of  claim 9 , wherein the light source body comprises a first substrate and a second substrate, and at least one of the first substrate and the second substrate is molded to form the plurality of discharge spaces. 
     
     
         11 . The surface light source device of  claim 1 , wherein the light source body comprises a flat first substrate and a flat second substrate between which a single discharge space is formed. 
     
     
         12 . The surface light source device of  claim 11 , wherein the electrodes are formed on at least one of the first and second substrates, and an aperture ratio of the electrode is 60% or more. 
     
     
         13 . A backlight unit comprising:
 a surface light source device comprising:
 a light source body having an inner space therein in which a discharge gas is contained, 
 a plurality of electrodes formed on the light source body in such a manner as to electrically divide the inner space into at least three blocks and applying discharge voltages to the blocks, and 
 a driving unit sequentially applying the discharge voltages to the blocks through the electrodes in synchronization with a video signal of an external display device; and 
 a case to receive the surface light source device. 
   
     
     
         14 . The backlight unit of  claim 13 , wherein the electrodes are formed at both ends of the blocks, and the driving unit applies anti-phase voltages to both ends of the blocks through the electrodes. 
     
     
         15 . The backlight unit of  claim 13 , wherein the driving unit comprises a plurality of inverters to applying the discharge voltages to the blocks through the electrodes.